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=head1 NAME

OPENSSL_ia32cap

=head1 SYNOPSIS

 extern unsigned long OPENSSL_ia32cap;
 unsigned long *OPENSSL_ia32cap_loc();

=head1 DESCRIPTION

OPENSSL_ia32cap is a variable containing IA-32 processor capabilities
bit vector as it appears in EDX register after executing CPUID
instruction with EAX=1 input value (see Intel Application Note
#241618). Naturally it's defined/meaningful on IA-32 platforms only.
The variable is normally set up automatically upon toolkit
initialization and can be manipulated afterwards to modify crypto
library behaviour. For the moment of this writing only two bits are
significant, namely bit #26 denoting SSE2 support, and bit #4 denoting
presence of Time-Stamp Counter. Resetting bit #26 at run-time for
example disables high-performance SSE2 code present in the crypto
library. You might have to do this if target OpenSSL application is
executed on SSE2 capable CPU, but under control of OS which does not
support SSE2 extentions. Even though you can programmatically
manipulate the value, you most likely will find it more appropriate to
set up an environment variable with the same name prior starting target
application, e.g. 'env OPENSSL_ia32cap=0x10 apps/openssl', to achieve
same effect without modifying the application source code.
Alternatively you can reconfigure the toolkit with no-sse2 option and
recompile.

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